Field of the Invention
This invention relates to improved oil soluble polymeric dispersant additives useful in oleaginous compositions, particularly oleaginous lubricating oil compositions. The additives, which are gel-free and substantially free from haze and cross-linking, comprise unsaturated homopolymers or interpolymers of C.sub.3 to C.sub.28 alpha-olefins, preferably interpolymers of ethylene with propylene or butene-1, which have been functionalized at unsaturated sites on the polymer chains and free-radically grafted with monounsaturated carboxylic reactant, e.g., maleic anhydride, preferably in a solvent such as lubricating oil, and then reacted with a nucleophilic post-treating reactant selected from (i) amine compounds containing only a single reactive amino group per molecule, (ii) alcohol compounds containing only a single hydroxy group per molecule, (iii) polyamine compounds containing at least two reactive amino groups per molecule, (iv) polyol compounds containing at least two reactive hydroxy groups per molecule, (v) aminoalcohol compounds containing at least one reactive amino group and at least one reactive hydroxy group per molecule, and (vi) mixtures of (i) to (v); provided that when said post-treating reactant includes one or more of (iii), (iv) or (v), the reaction between the grafted polymer and the nucleophilic post-treating reactant is conducted in the presence of sufficient chain-stopping or end-capping co-reactant to ensure that the grafted and post-reacted product mixture is gel-free.
In one embodiment of the invention, .alpha.-olefin homopolymers and interpolymers, prior to being functionalized have a number average molecular weight of from about 700 to about 10,000; and prior to being grafted with monounsaturated carboxylic reactant to randomly attach carboxylic acid producing moieties along the polymer chains, are functionalized at sites of carbon-to-carbon unsaturation such that at least about 75% of the functionalized polymer chains are monofunctional, i.e., contain one functional group such as an acid, anhydride or ester group.
In a preferred aspect of the invention, the unsaturated .alpha.-olefin homopolymers and interpolymers are functionalized by means which selectively attach functional groups to the polymer chains only at sites containing ethylenic unsaturation, such as, for example, by a thermal "ene" reaction or a Koch reaction.
In still other preferred aspects of the invention, the .alpha.-olefin homopolymers and interpolymers, prior to being functionalized, are characterized in that at least about 30 percent, and preferably at least about 60 percent of the polymer chains possess terminal ethenylidene, i.e., vinylidene, unsaturation.
Ashless ester and nitrogen containing lubricating oil dispersants have been widely used by the industry. Typically, these dispersants are prepared from a long chain hydrocarbon polymer by reacting the polymer with maleic anhydride to form the corresponding polymer which is substituted with succinic anhydride groups. Polyisobutylene has been widely used as the polymer of choice, chiefly because it is readily available by cationic polymerization from butene streams (e.g., using AlCl.sub.3 catalysts). Such polyisobutylenes generally contain residual unsaturation in amounts of about one ethylenic double bond per polymer chain, positioned along the chain.
The polyisbutylene polymers (PIB) employed in most conventional dispersants are based on a hydrocarbon chain of a number average molecular weight (M.sub.n) of from about 900 to about 2500. PIB having a M.sub.n of less than about 300 gives rather poor performance results when employed in dispersants because the molecular weight is insufficient to keep the dispersant molecule fully solubilized in lubricating oils. On the other hand, high molecular weight PIB (M.sub.n &gt;3000) becomes so viscous that conventional industrial practices are incapable of handling this product in many operations. This problem becomes much more severe as the PIB molecular weight increases to 5,000 to 10,000.
Increased amounts of terminal ethylenic unsaturation in polyisobutylene (so-called "reactive polyisobutylene") has been achieved by BF.sub.3 catalyzed polymerization of isobutylene. Exemplary of references disclosing these polymers is U.S. Pat. No. 4,152,499. However, such reactive polyisobutylene materials can still contain substantial amounts of unsaturation elsewhere along the chain. Further, it is difficult to produce such reactive polyisobutylene polymers at molecular weights of greater than about 2,000, and, even so, the reactive polyisobutylenes themselves still suffer the above-noted viscosity increase disadvantages as molecular weights are increased.
Other polymers, such as ethylene-alpha-olefin interpolymers, (e.g., ethylene-propylene copolymers and terpolymers containing non-conjugated dienes), have been disclosed as suitable polymers for the preparation of ashless dispersants.
U.S. Pat. No. 4,234,435, for example, discloses dispersants prepared from polyalkenes, M.sub.n of 1,300 to about 5,000. The polyalkene can comprise homopolymers or interpolymers of C.sub.2 to C.sub.16 terminal olefins, of which ethylene-propylene copolymers are said to be examples, with specific reference to a copolymer of 80% ethylene and 20% propylene.
However, ethylene-alpha-olefin interpolymers of the above molecular weights could be produced using Ziegler-Natta catalysts only in combination with H.sub.2 as molecular weight control in order to terminate the growing copolymer chains within this molecular weight range. Without use of H.sub.2 or other conventional, so-called "chain-stoppers", the interpolymers produced with Ziegler-Natta catalysts would tend to have molecular weights greatly in excess of the above range. (Such higher copolymers, for example, are widely employed in ungrafted form as viscosity index improvers, and when grafted with nitrogen-containing groups, as described below, are conventionally employed as dispersant-viscosity index improver polymers.) The use of H.sub.2 as a chain stopper has the disadvantage of causing the saturation of the olefinic double bond content of the copolymer. Thus, while lower molecular weight copolymers were theoretically possible to prepare, their low unsaturation content (and the accompanying low graft copolymer yields) would have made their further functionalization by a thermal "ene" reaction, e.g., with dicarboxylic acid moieties in preparing dispersants, highly unattractive.
High molecular weight ethylene-propylene copolymer and ethylene-propylene-diene terpolymers, having viscosity average molecular weights of from about 20,000 to 300,000, are generally produced employing Ziegler catalysts, generally VCl.sub.4 or VOCl.sub.3 with a halide source, such as organoaluminum halides and/or hydrogen halides. Such high molecular weight EP and EPDM polymers find use as viscosity index improvers. See, e.g., U.S. Pat. Nos. 3,563,964; 3,697,429; 4,306,041; 4,540,753; 4,575,574; and 4,666,619.
The concept of functionalizing V.I. improving high molecular weight ethylene copolymers, with acid moieties such as maleic anhydride, followed by derivatizing with an amine, to form a V.I.-dispersant oil additives is known in the art as indicated by the following patents.
U.S. Pat. No. 3,316,177 teaches ethylene copolymers of at least 50,000, such as ethylene-propylene, or ethylene-propylene-diene, which are heated to elevated temperatures in the presence of oxygen so as to oxidize the polymer and cause its reaction with maleic anhydride which is present during the oxidation. The resulting polymer can then be reacted with alkylene polyamines.
U.S. Pat. No. 3,326,804 teaches reacting ethylene copolymers with oxygen or ozone, to form a hydroperoxidized polymer which is grafted with maleic anhydride followed by reaction with polyalkylene polyamines. Preferred are ethylene-propylene copolymers, having M.sub.v from 100,000 to 500,000, prepared by Ziegler type catalysts.
U.S. Pat. No. 4,160,739 teaches an ethylene copolymer (M.sub.v =10,000 to 200,000) which is grafted, using a free radical technique, with alternating maleic anhydride and a second polymerizable monomer such as methacrylic acid, which materials are reacted with an amine having a single primary, or a single secondary, amine group.
U.S. Pat. No. 4,161,452 relates to graft copolymers wherein the backbone polymer is a polymeric hydrocarbon such as EP copolymer or EPDM (M.sub.v =10,000 to 200,000) and the grafted units are the residues of an additional copolymerizable monomer system comprising, e.g., maleic anhydride, and at least one other addition monomer.
U.S. 4,171,273 reacts an ethylene copolymer (M.sub.v =10,000 to 100,000) with maleic anhydride in the presence of a free radical initiator and then with mixtures of C.sub.4 to C.sub.12 n-alcohol and amine such as N-aminopropylmorpholine or dimethylamino propyl amine to form a V.I.-dispersant-pour depressant additive.
The following references include disclosures of EP/EPDM polymers of M.sub.v of 700/500,000, also prepared by conventional, e.g., Ziegler catalysts.
U.S. Pat. No. 4,089,794 teaches grafting the ethylene copolymer (M.sub.n =700 to 500,000) with maleic anhydride using peroxide in a lubricating oil solution, wherein the grafting is preferably carried out under nitrogen, followed by reaction with polyamine.
U.S. Pat. No. 4,137,185 teaches reacting C.sub.1 to C.sub.30 monocarboxylic acid anhydrides, and dicarboxylic anhydrides, such as acetic anhydride, succinic anhydride, etc., with an ethylene copolymer (M.sub.n =700 to 500,000) reacted with maleic anhydride and a polyalkylene polyamine to inhibit cross linking and viscosity increase due to further reaction of any primary amine groups which were initially unreacted. Similar to U.S. Pat. No. 4,137,185 is E.P. Application 295,854 A2, wherein a C.sub.12 to C.sub.18 hydrocarbyl substituted succinic anhydride is used to treat the imidized, carboxylic-grafted ethylene-alpha-olefin in a separate and subsequent reaction step.
U.S. Pat. No. 4,144,181 is similar to 4,137,185 in that it teaches using a sulfonic acid to inactivate the remaining primary amine groups when a maleic anhydride grafted ethylene-propylene copolymer (M.sub.n =700 to 500,00) is reacted with a polyamine.
U.S. Pat. No. 4,219,432 teaches maleic anhydride grafted ethylene copolymer (M.sub.n =700 to 500,00) reacted with both a first amine having only one primary group and a second amine having two or more primary groups. More particularly, the grafted copolymer is reacted partially (i.e., between about 10 to 90% conversion) with a tertiary amino-amine compound having one primary amine group, and then fully with an alpha-omega primary diamine having two primary amine groups. Then, in a post-reaction step, the imidized polymer is reacted with an anhydride of an organic acid (e.g., a C.sub.1 -C.sub.30 hydrocarbyl substituted carboxylic acid). The treatment of the imidized polymer by reaction with the organic acid anhydride stabilizes the polymer for use as a dispersant/VI improver additive and inhibits viscosity increase of the lubricating oil compositions in which it is used.
U.S. Pat. No. 4,505,834 teaches VI improver/dispersant additives for lubricating oils produced by grafting succinic groups onto an ethylene .alpha.-olefin polymer in a hydrogen-treated mineral oil solution, and then reacting the grafted intermediate with an amine having only one primary amine group. The succinic groups are grafted onto the copolymer by reacting the copolymer with maleic acid, anhydride, or acid-ester in the presence of a free radical producing catalyst. The patent particularly discloses that the use of an amine that contains only one primary amine group "prevents the amine from acting as a crosslinking agent between maleic grafted olefin copolymer." (column 3, lines 24-25) The ethylene-alpha-olefin copolymer has a number average molecular weight of about 1,000-500,000 and contains about 30-80 wt. % ethylene units and 20-70 wt. % olefin units, and may optionally contain up to about 10 Wt. % non-conjugated diene units.
U.K. Application 2,055,852 A discloses a process for the production of polymeric dispersant additives and viscosity index improvers for lubricating oils, wherein an ethylene-alpha-olefin copolymer in mineral oil solution is grafted under an inert atmosphere with an ethylenically unsaturated dicarboxylic acid material in the presence of a free radical initiator to provide a grafted copolymer that contains from 2 to 20 carboxyl groups per copolymer molecule, and wherein the grafted copolymer is then imidated by reaction with 0.5 to 1.5 moles of an alkyl hetero-substituted alkylene primary amine per mole of grafted dicarboxylic acid groups. In this process, a portion of the mineral oil is grafted and imidated as well. Lubricating oil compositions containing these additives are said to be viscosity-stable and haze-free. The copolymers which are grafted contain from about 2 to 98 wt. % ethylene and from about 2 to 98 wt. % of one or more C.sub.3 -C.sub.28 .alpha.-olefins. The copolymers preferably have a crystallinity of less than 25 wt. % and a M.sub.n of about 700 to about 500,000.
E.P. Application 171,167 A2 discloses a process for grafting oil soluble hydrocarbon polymers or copolymers of M.sub.n from 5,000 to 500,000 with an ethylenically unsaturated C.sub.3 -C.sub.10 carboxylic acid having 1 to 2 carboxylic acid groups or an anhydride group in the presence of a free radical initiator and a chain stopping agent. A preferred group of polymers are ethylene-alpha-olefin copolymers that contain 15-90 wt. % ethylene and 10-85 wt. % of one or more C.sub.3 -C.sub.28 .alpha.-olefins. The grafting is accomplished in the solid state, rather than in solution, to avoid grafting the solvent. A VI improver/dispersant may be obtained by dissolving the grafted material in a mineral lubricating oil and reacting it with an amine having 2-60 carbons atoms and 1-12 amine groups. Especially preferred amines have "a single primary amine group, with any other amine groups present being tertiary amine groups. This minimizes cross-linking and becomes particularly important when the polymer has a relatively high degree of acidity, e.g. above about 0.1 meq./g of polymer." (page 17, lines 5-9)
U.S. Pat. No. 4,749,505 discloses a process for the molecular weight degradation of olefin polymers of M.sub.n of from about 5,000 to about 500,000, in which the polymer is heated in the present of a free radical initiator under inert atmosphere and in the substantial absence of a solvent. Suitable olefin polymers include copolymers of two or more monomers of C.sub.2 to C.sub.30 alpha-olefins. A VI-dispersant additive may be formed from the degraded polymer by grafting the hydrocarbon polymer with an ethylenically unsaturated C.sub.3 -C.sub.10 carboxylic acid having 1 or 2 carboxylic acid groups or an anhydride group before, during or after the degradation step, and then reacting the grafted polymer with an amine. Useful amines include mono- and polyamines of about 2-60 carbon atoms and about 1-12 nitrogen atoms. Especially preferred are amines "having a single primary amine group, with an other amine groups present being tertiary amine groups" to inhibit crosslinking. (column 7, lines 16-18)
U.S. Pat. No. 4,863,623 teaches a multifunctional lubricant additive, which acts as a VI improver, a dispersant, and an anti-oxidant in lubricating oil compositions. The multifunctional additive comprises an ethylene copolymer or terpolymer of a C.sub.3 -C.sub.10 alpha-monoolefin and optionally a non-conjugated diene or triene that has been grafted with a ethylenically unsaturated carboxylic function, and then further derivatized with an amino-aromatic polyamine compound. The process for grafting the unsaturated carboxylic function, preferably maleic anhydride, onto the copolymer may be a thermal "ene" process or a free radical process, either in solution or in solid form. The ethylene copolymer is oil soluble, substantially linear, and has an average molecular weight from about 5,000 to 500,000. Among the suitable copolymers are ethylene-alpha-olefin copolymers having from about 15-80 mole % ethylene and 20-85 mole % of an alpha-olefin.
E.P. Application 396,297 A1 contains teachings similar to that of the above-described U.S. Pat. No. 4,863,623, with the significant difference being that the polymers subjected to grafting with the carboxylic compound have molecular weights in a lower range, from 300 to 3,500. Two other patents along similar lines to U.S. Pat. No. 4,863,623 are Canadian Patent 2,021,959 and U.S. Pat. No. 5,075,383, both of which are directed to dispersant-antioxidant additives prepared by grafting ethylene-alpha-olefin copolymers with an acylating agent before or after the molecular weight degradation of the copolymer, followed by derivatization of the grafted copolymer with an aromatic polyamine.
The following references include disclosures of lubricating oil additives produced from ethylene-alpha-olefin interpolymers, radically grafted with unsaturated carboxylic compounds, by reaction with amine reactants in the presence of hydrocarbyl-substituted carboxylic acid compounds acting as chain-stoppers:
U.S. Pat. No. 4,557,847 teaches polymeric viscosity index improver-dispersant additives for lubricating oils produced by reacting an ethylene-alpha-olefin copolymer grafted with an ethylenically unsaturated carboxylic material having 1 or 2 carboxylic acid groups or anhydride groups, preferably maleic anhydride, with an alkylene or oxyalkylene amine having at least two primary amine groups and a branched chain acid. The ethylene-alpha-olefin copolymer has a M.sub.n of from about 5,000 to about 500,000. Copolymers containing one or more diolefins are also suitable. The branched chain acid may be of formula RCOOH where R is a hydrocarbyl group containing 20-148 carbon atoms. The grafted copolymer, the amine, and the branched acid may be reacted together, or the amine and branched acid may be reacted to form a pre-reacted product which is then reacted with the grafted copolymer. The specification discloses that "[c]ross-linking between ethylene copolymer molecules is reduced or inhibited since many of the polyamine molecules will have one primary group reacted with a maleit anhydride moiety of the ethylene copolymer, while its other primary group is reacted with the branched chain acid component." (column 2, lines 32-38).
U.S. Pat. No. 4,517,104, which has teachings similar to those in U.S. Pat. No. 4,557,847, discloses a broader range of acid components suitable for use as the co-reactant with the amine. More particularly, the acid component may be a C.sub.12 -C.sub.49 hydrocarbyl substituted succinic anhydride or acid, a long-chain monocarboxylic acid of formula RCOOH where R is a C.sub.50 -C.sub.400 hydrocarbyl group, or a long-chain C.sub.50 -C.sub.400 hydrocarbyl substituted succinic anhydride or acid. Also along similar lines to U.S. Pat. No. 4,517,104 are E.P. Application 352,072 A1, which discloses the use of an acid component comprising a long chain hydrocarbyl substituted dicarboxylic acid material and a short chain hydrocarbyl substituted dicarboxylic acid or anhydride, and E.P. Application 369,674 A1, which discloses a poly-n-butene substituted dicarboxylic acid material of M.sub.n 300-3,000 as the acid-component.
Related disclosures of maleic anhydride grafted, aminated ethylene-propylene polymer viscosity improver-dispersant additives useful in lubricating oil compositions are contained in U.S. Pat. Nos. 4,507,515; 4,632,769; 4,693,838; and 4,707,285.
U.S. Pat. No. 4,668,834 discloses the preparation (via certain metallocene and alumoxane catalyst systems) of ethylene-alpha olefin copolymers and terpolymers having vinylidene-type terminal unsaturation, which are disclosed as being useful as intermediates in epoxy-grafted encapsulation compositions.
U.S. Pat. No. 4,704,491 relates to liquid ethylene alpha-olefin random copolymers, which are useful when hydrogenated, as synthetic lubricant oil. The copolymers are characterized, inter alia, by having 10-85 mol. % ethylene units, 15-90 mol. % alpha-olefin units, M.sub.n of from 300 to 10,000 and a M.sub.w /M.sub.n of not more than 2.5. The patent also indicates that the liquid copolymer can be modified easily since it has a double bond capable of reacting with maleic anhydride, etc., at the molecular chain ends.
Japanese Published Patent Application 87-129,303 A relates to narrow molecular weight distribution (M.sub.w /M.sub.n &lt;2.5) ethylene alpha-olefin copolymer waxes containing 85-99 mol. % ethylene, which are disclosed as being useful as dispersing agents, modifiers or materials to produce toners. The copolymers (having crystallinity of from 5-85%) are prepared in the presence of a catalyst system comprising Zr compounds having at least one cycloalkadienyl group and alumoxane.
European Patent 128,046 discloses (co)polyolefin reactor blends of polyethylene and ethylene higher alpha-olefin copolymers prepared by employing described dual-metallocene/alumoxane catalyst systems.
European Patent Publication 129,368 discloses metallocene/alumoxane catalysts useful for the preparation of ethylene homopolymer and ethylene higher alpha-olefin copolymers.
European Patent Application Publication 257,696 A1 relates to a process for dimerizing alpha-olefins using a catalyst comprising certain metallocene/alumoxane systems.
European Patent Publication 305,022 A1 relates to certain synthetic hydrocarbon lubricating oil compositions containing a load-withstanding additive and a liquid ethylene alpha-olefin random copolymer modified by graft copolymerization with an unsaturated carboxylic acid or derivative thereof (e.g., maleic anhydride). The ethylene alpha-olefin copolymers (M.sub.n of 300 to 12,000) are obtained using Ziegler catalysts (e.g., catalyst formed from soluble V compound and an organoaluminum compound), and are grafted in the presence of a free radical initiator.
PCT Published Patent Application WO 88/01626 relates to transition metal compound/alumoxane catalysts for polymerizing alpha-olefins.
European Patent Publication 148,592 A2 relates to a hydroformylation process for producing carboxylic ester and/or carboxylic acid functionalized derivatives of polymeric compounds, such as polyisobutylenes and ethylene .alpha.-olefin copolymers containing residual carbon--carbon double bonds. The process described in that publication involves reacting the polymeric compound with carbon monoxide and an alcohol in the presence of protonic acid and a catalyst system comprising a copper compound and at least one metal (or compound thereof) selected from palladium, rhodium, ruthenium, iridium or cobalt.
Barhrmann et al., (New Syntheses with Carbon Monoxide, Reactivity and Structure Concepts in Organic Chemistry, Vol. 11, pp. 372-413, Springer-Verlag 1980) discloses a two-stage Koch syntheses of carboxylic acids from olefins, carbon monoxide and water in the presence of an acid catalyst. In the first stage, the olefin reacts with the acid catalyst and carbon monoxide in the absence of water, then in the second stage the complex formed by the olefin, carbon monoxide and catalyst is hydrolyzed. The two stages can be illustrated by the following equation: ##STR1##
The reaction occurs between -20.degree. and 80.degree. C. and pressures up to 100 bar; and suitable acid catalysts include H.sub.2 SO.sub.4, H.sub.3 PO.sub.4, HF or Lewis acids such as BF.sub.3. There is no suggestion that the olefins used in this reaction might comprise .alpha.-olefin polymers having a number average molecular weight of from about 700 to 10,000.